Device for imparting continuous passive motion to human joints

ABSTRACT

A portable apparatus for imparting continuous passive motion to a human joint. A support is provided for harnessing to parts of the body at one side of the joint and conveyor means movable relative to the support is provided for connection to a part at the other side of the joint, so that the latter forms a link which is flexed as the conveyor means moves back and forth relative to the support. Drive means insures that a substantially continuous slow rhythmic reciprocating movement is applied to the joint.

This is a division of application Ser. No. 362,896 filed Mar. 29, 1982,now U.S. Pat. No. 4,487,199.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a portable prosthetic device used to treat ahuman joint by applying "continuous passive motion".

2. Description of the Prior Art

Dr. Robert B. Salter, Professor and Head of Orthopaedic Surgery at theUniversity of Toronto, and Senior Orthopaedic Surgeon at the Hospitalfor Sick Children in Toronto, first developed the concept and coined theexpression "continuous passive motion". Dr. Salter's work is describedin the article "Joints Were Meant to Move--And More Again" by Ohlendorfin "The Graduate", published by The Department of Information Services,University of Toronto, September/October 1980.

Briefly, according to this concept, a human joint, for example, a knee,elbow, or finger joint, is kept under slow continuous constrained motionas distinct from being held motionless or being moved intermittently.Keeping an injured or post operative joint mobile rather thanimmobilizing it in a cast is beneficial to the cartilage.

Attempts which have been made to provide machines that exercise jointsare designed for intermittent operation and do not supply continuouspassive motion. Moreover, they are usually too heavy and bulky to bereadily portable and thus to be mounted on the body.

A primary aim of the present invention is to provide an apparatus whichimparts continuous motion to the joint and which is portable so that itcan be mounted on the patient's body.

SUMMARY OF THE INVENTION

An apparatus, according to the invention, includes a support structure,usually a housing containing working parts. Harness means mounts thesupport structure on the patient's body or, in an alternativearrangement, the support structure may be mounted on a crutch or bed.Traveller means is carried by the housing for reciprocating movementrelative to it and is connected to an extremity of the limb having thejoint to be exercised so that the joint completes the linkage. Motormeans in the housing drives the traveller means back and forth through apredetermined stroke with a slow rhythmic motion.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the invention, it will be referred tomore specifically by reference to the accompanying drawings, whichillustrate preferred embodiments, and in which:

FIG. 1 is a perspective view showing a unit for treating an elbow joint;

FIG. 2 is a greatly enlarged fragmentary perspective view showing thewrist connection in the unit of FIG. 1;

FIG. 3 is a schematic perspective diagram, of an exploded nature,showing the arrangement of the parts in a unit;

FIG. 4 is a side elevation showing a unit for treating the knee joint inwhich the unit forms part of a crutch;

FIG. 5 is a side elevation of a variation of the unit of FIG. 4;

FIG. 6 is a fragmentary perspective showing an operating unit fortreating the knee joint and which is connected to a bed on which thepatient is reclining;

FIG. 7 is a fragmentary perspective view showing a unit for treating afinger or thumb joint;

FIG. 8 is a perspective view of the unit shown in FIG. 7, illustratingthe drive mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring more particularly to FIG. 1, the device is made up of asupport structure which, in this case, is an elongated housing Aconnected to the shoulder by a harness B and to the waist by a belt D.Actuator or traveller means, movable relative to the housing, isconnected to the wrist by a cuff C. The traveller means is supported bythe housing for linear reciprocating movement relative to it. Motormeans drives the traveller means back and forth through a predeterminedstroke in a slow rhythmic cycle. This imparts a correspondingreciprocating motion to the arm thus imparting continuous passive motionto the elbow joint.

The speed of movement of the actuator means would, in the embodimentshown, range from one-half foot to four feet per minute, or fromone-third to two cycles per minute.

In order to supply supination and pronation to the wrist, the cuff C isconnected (see FIG. 2) to a special mechanism. Mounted for rotation on aU-shape bracket 15 is a shaft 17, carrying a bevel gear 19, which mesheswith a crown gear 21, carried on a hub 23, mounted on a plate 25 forminga part of the traveller means.

The plate 25 moves back and forth, along the housing A, and the flexingof the elbow causes rotation of the arm at the wrist, by virtue of itsconnection to the bevel gear 19 as it is caused to ride around the crowngear 21. At the same time, the wrist is held to the plate 25 so that itmakes longitudinal movements with the latter along the housing A.

FIG. 3 shows in detail the support housing, actuating means, motor meansand associated parts. A motor 31 drives an elongated screw 33 whoseopposite end is rotatably held in a recirculating ball-type nut 32. Acylindrical slide 35 is connected to the nut 32 and moves linearly underthe drive of the screw 33 between the limiting stops 37 and 39, whichare locked to the housing A by thumb screws.

The mechanism is encased in an outer tube 41 and an inner concentrictube 42. The tube 41 is provided with a longitudinal slot 43 and theconcentric tube 42 with an elongated slot 45. The slot 43 accommodatesthe flange connection 48 between the slide 35 and the plate 25. The slot45 accommodates the flange connection 46 between the ball nut 33 and theslide 35.

The motor 31 is powered by batteries 47 which operate through circuitson a circuit board 49 and is governed by controls 51. The tube 41 isprovided with a gooseneck part 53 about which there extends a bracket 55connecting it to the harness B. The other end of the tube 41 has aterminal 56 provided with an eye 57 so that it can be hung from asuitable hook when required.

The motor 31 is a reversible motor. It will reverse as soon as anexcessive load is applied. This may be, for example, where the actuatoror traveller reaches the end of its stroke and is halted by the stop 37or 39 as the case may be. Or, it may be where there is some unplannedobstruction, for example, sheets jamming in the mechanism or where thepatient offers undue resistance. A safety function is thus performed aswell as a prime actuating function.

Examples of suitable motors are geared D.C. Brush type motors made byFaulhaber, Escap, and Maxon Precision, all of Switzerland.

FIG. 4 describes an apparatus for flexing the knee joint. Similarnumbers have been applied to similar parts, as on FIGS. 1 and 3, withthe exception that they have been raised by 100 and the letters havebeen given a subscript 1.

In this case, the support housing A₁ forms part of a crutch forsupporting the patient and embodies operating mechanism similar to thatshown in FIG. 3, except that the housing A₁ is straight instead ofhaving a gooseneck end. It has a rubber foot 157 taking the place of theterminal 56. A handle B₁ takes the place of the harness B and isprovided with an armpit bar 159. The part B₁ slides on the top end ofthe support housing A₁. Taking the place of the plate 25 is a simplefoot plate with straps, as compared with the supination and pronationmechanism for rotating the wrist.

FIG. 5 shows an alternative arrangement in which a waistband B₂ isemployed to connect the top of a support housing A₂ to the body. Aseparate crutch D supports the patient.

FIG. 6 illustrates a further form of leg exercising device. In thiscase, the support housing of FIGS. 4 and 5 is connected to a bed. It isretained by spaced-apart brackets 61 and 62. The leg of a patient lyingon the bed is connected to the foot plate as in FIGS. 4 and 5.

FIG. 7 illustrates a device for flexing finger or thumb joints. Hereagain a support housing A₄ is connected to a cuff B₄ mounted on thewrist and hand in place of the harness of FIG. 1. An actuator wire 425moves back and forth from the housing A₄, through a flexible guide tube441, to a connection with the thumb.

The connection from the actuator wire 425 to the thumb is through ahinge 443 to a small plate 445, adhesively connected to the thumbnail.Alternatively, the actuator member 445 can be connected to any of thefingers or several fingers at a time.

A mechanism for moving the actuator wire 425 is shown in FIG. 8. Thesupport structure is fashioned from a block of plastic in which recesseshave been made to accommodate the various parts. A geared motor 447drives a sprocket 432 about which there is trained a chain 433 which isalso trained about a spaced-apart sprocket 435. The actuator wire 425 isconnected at 427 to one of the links of the chain 433. Batteries 446 areaccommodated within the block as is an operating switch 451. The motormoves the chain continuously so that the actuator wire 425 moves in onedirection along the top run of the chain and then down along the bottomrun in the other direction so as to impart substantially continuousreciprocating movement to the wire 425 and consequently to the handjoint.

From this detailed description it will be evident that variousmodifications can be made within the spirit of the invention to treatvarious joints of the body under appropriate conditions.

I claim:
 1. An actuator for imparting back and forth motion in a slowrhythmic cycle, comprising,a support housing having a longitudinal slotdefining a guide track, a traveller operatively mounted to said supporthousing for back and forth motion relative to said housing, a tubularhousing mounted in said support housing, said tubular housing having alongitudinally extending slot offset relative to said guide track, and adrive member mounted inside said tubular housing adapted to drive saidtraveller with said back and forth motion, said traveller including atravel element mounted inside said support housing operatively connectedthrough the longitudinally extending slot in said tubular housing tosaid drive member, said travel element being connected to a travelmember mounted for travel along said guide track.
 2. An actuatoraccording to claim 1, further including motor means to drive member,said motor means being housed inside said housing.
 3. An actuatoraccording to claim 1, wherein said tubular housing is centrally disposedin said support housing and said drive member is centrally disposed insaid tubular housing.
 4. An actuator according to claim 1, wherein saiddrive member comprises a drive screw having a screw thread mounted forrotation inside said tubular housing, and said travel element is mountedon said drive screw for movement relative to said thread, said travelelement being restrained against rotary movement with said drive screwsuch that rotary movement of said drive screw is converted intolongitudinal movement of said travel element whereby said travel membermoves along said guide track.
 5. An actuator according to claim 4,wherein said travel element comprises nut means mounted on said drivescrew.
 6. An actuator according to claim 4, wherein said travel elementcomprises an inner nut member mounted on said drive screw, inside saidtubular housing, and an outer member held to said nut member byconnecting means extending through said longitudinal slot in saidtubular housing, said outer member being mounted to travel between saidsupport housing and said tubular housing, and including a pair ofspaced-apart terminal stops in said support housing to define saidpredetermined stroke.
 7. An actuator according to claim 6, furtherincluding motor means to drive said drive screw, said motor beingreversible, whereby it drives the traveller first in one direction andthen in the other to cause reciprocating movement of the traveller. 8.An actuator according to claim 7, including means to reverse thedirection of the motor within said predetermined stroke, when apredetermined excessive load is applied to said motor means during saidtravel stroke.
 9. An actuator according to claim 8, wherein said meansto reverse the direction is actuatable by predetermined resistance ofthe screw member to rotation.
 10. An actuator according to claim 9,wherein said motor means is housed inside said support housing.
 11. Anactuator according to claim 4, wherein said tubular housing is centrallydisposed in said support housing and said drive screw is centrallydisposed in said tubular housing.
 12. An actuator according to claim 1,further including means for reversing the direction or travel of saidtraveller, when a predetermined load is applied to said traveller,during said back and forth motion.